U.S. patent application number 11/313118 was filed with the patent office on 2007-06-21 for display units, display devices, and repair methods for convering a bright dot to a dark dot in same.
This patent application is currently assigned to TOPPOLY OPTOELECTRONICS CORP.. Invention is credited to Chien-Yi Hsu, Yi-Hsing Lee, I-Wei Wu.
Application Number | 20070139330 11/313118 |
Document ID | / |
Family ID | 38172837 |
Filed Date | 2007-06-21 |
United States Patent
Application |
20070139330 |
Kind Code |
A1 |
Wu; I-Wei ; et al. |
June 21, 2007 |
Display units, display devices, and repair methods for convering a
bright dot to a dark dot in same
Abstract
A display unit for a display panel. The display unit comprises a
switch unit, a liquid crystal capacitance, and a storage capacitor.
The switch unit has a control terminal coupled to a scan line, an
input terminal coupled to a data line, and an output terminal
coupled to a pixel electrode. The liquid crystal capacitance is
coupled between the pixel electrode and a common electrode
receiving a common-voltage signal. The storage capacitor is coupled
to the pixel electrode and a reference electrode receiving a
low-gate signal. The level of the common-voltage signal is
different from that of the low-gate signal.
Inventors: |
Wu; I-Wei; (Hsinchu, TW)
; Hsu; Chien-Yi; (Hsinchu City, TW) ; Lee;
Yi-Hsing; (Keelung City, TW) |
Correspondence
Address: |
LIU & LIU
444 S. FLOWER STREET, SUITE 1750
LOS ANGELES
CA
90071
US
|
Assignee: |
TOPPOLY OPTOELECTRONICS
CORP.
|
Family ID: |
38172837 |
Appl. No.: |
11/313118 |
Filed: |
December 19, 2005 |
Current U.S.
Class: |
345/90 |
Current CPC
Class: |
G09G 2330/10 20130101;
G09G 3/3677 20130101; G09G 2300/0876 20130101 |
Class at
Publication: |
345/090 |
International
Class: |
G09G 3/36 20060101
G09G003/36 |
Claims
1. A display unit for a display panel having a display array formed
by at least one data line and at least one scan line, comprising: a
switch unit having a control terminal coupled to the scan line, an
input terminal coupled to the data line, and an output terminal
coupled to a pixel electrode; a liquid crystal capacitance coupled
between the pixel electrode and a common electrode receiving a
common-voltage signal; and a storage capacitor coupled to the pixel
electrode and a reference electrode receiving a low-gate signal;
wherein a voltage level of the common-voltage signal is different
from that of the low-gate signal.
2. The display unit as claimed in claim 1, wherein the voltage
level of the low-gate signal is lower than that of the
common-voltage signal.
3. The display unit as claimed in claim 1, wherein the scan line
turns on the switch unit with a first voltage and turns off that
with a second voltage.
4. The display unit as claimed in claim 3, wherein the level of the
low-gate signal is equal to the second voltage.
5. The display unit as claimed in claim 4, wherein the switch unit
is an N-type transistor or a P-type transistor.
6. A repair method for converting a bright dot to a dark dot in a
display unit comprising a switch unit having a control terminal
coupled to a scan line, an input terminal coupled to a data line,
and an output terminal coupled to a pixel electrode, a liquid
crystal capacitance coupled between the pixel electrode and a
common electrode, and a storage capacitor coupled to the pixel
electrode and a reference electrode, the method comprising:
disconnecting the input terminal of the switch unit from the data
line or output terminal from the switch unit; and connecting the
pixel electrode and the reference electrode together; wherein, a
voltage level on the common electrode and a voltage level on the
reference electrode are different.
7. The method as claimed in claim 6, wherein the voltage level of
the reference electrode is lower than the voltage level of the
common electrode.
8. The method as claimed in claim 6, wherein the scan line turns on
the switch unit with a first voltage and turns off that with a
second voltage.
9. The method as claimed in claim 8, wherein the voltage level on
the reference is equal to the second voltage.
10. The method as claimed in claim 9, wherein the switch unit is an
N-type transistor or a P-type transistor.
11. A display panel, comprising: a display array formed by a
plurality of data lines and a plurality of scan lines and
comprising a plurality of display units as claimed in claim 1,
wherein the scan lines are interlaced with the data lines.; a data
driver controlling the data lines; and a scan driver controlling
the scan lines.
12. A display device, comprising: a display panel as claimed in
claim 11; and a controller, wherein the controller is operatively
coupled to the display panel.
13. An electronic device, comprising: a display device as claimed
in claim 12; and an input unit, wherein the input unit is
operatively coupled to the display device.
14. The electronic device as claimed in claim 13, wherein the
electronic device is a PDA, a display monitor, a notebook computer,
a tablet computer, or a cellular phone.
15. A display unit for a liquid crystal display panel, comprising:
a liquid crystal capacitance biased at a first voltage potential; a
storage capacitor operatively coupled in parallel to the liquid
crystal capacitance, and biased at a second voltage potential,
wherein the first and second voltage potentials are different; and
a switch unit commonly coupled to the parallel coupled liquid
crystal capacitance and storage capacitor.
16. The display unit as in claim 15, wherein the storage capacitor
and the liquid crystal capacitance are commonly coupled at one end
to the switch unit, and at the other end separately to different
voltages.
17. The display unit as in claim 15, further comprising a data line
and a scan line, wherein the switch unit is also operatively
coupled to the scan line and data line.
18. The display unit as in claim 17, wherein the switch unit
comprises a transistor having a source and drain, and wherein in
the event of a short between the drain and source of the
transistor, the source or drain is decoupled from the rest of the
circuit, and the storage capacitor is shorted, so as to maintain a
voltage potential difference across the liquid crystal
capacitance.
19. The display unit as in claim 18, wherein the voltage difference
is difference between the first and second voltage potentials.
20. The display unit as in claim 19, wherein the first voltage
potential is higher than the second voltage potential.
Description
BACKGROUND
[0001] The present invention relates to a display unit, and in
particular to a repair method for a bright dot in a display
unit.
[0002] FIG. 1a is a schematic diagram of a conventional liquid
crystal display (LCD) panel. As shown in FIG. 1a, the LCD panel 1
comprises a data driver 10, a scan driver 11, and a display array
12. The data driver 10 controls a plurality of data lines D.sub.1
to D.sub.m, and the scan driver 11 controls a plurality of scan
lines G.sub.1 to G.sub.n. The display array 12 is formed by
intersecting data lines D.sub.1 to D.sub.m and scan lines G.sub.1
to G.sub.n. The interlaced data line D.sub.m and scan line G.sub.n
correspond to a display unit, for example, the interlaced data line
D.sub.1 and scan line G.sub.1 correspond to a display unit 100. For
each display unit, the equivalent circuit of the display unit 100
comprises a thin film transistor (TFT) T10, a storage capacitor
Cs10, and a liquid crystal capacitance Clc10. The TFT T10 has a
gate terminal coupled to the scan line G.sub.1, a drain terminal
coupled to the data line D.sub.1, and a source terminal coupled to
a pixel electrode PE. The storage capacitor Cs10 is coupled between
the pixel electrode PE and a reference electrode RE and stores
voltage of a video signal. The liquid crystal capacitance Clc10 is
coupled between the pixel electrode PE and a common electrode CE.
In conventional LCD processes, the reference electrode RE and the
common electrode CE are coupled and both receive a common voltage
Vcom.
[0003] FIG. 1b is a schematic diagram of voltage coupled to scan
lines G.sub.1 to G.sub.n and common voltage coupled to the common
electrodes. Referring to FIGS. 1a and 1b, the scan driver 11
sequentially outputs scan signals to scan lines G.sub.1 to G.sub.n
according to a scan control signal. When receiving a scan signal
with a high-gate voltage Vhi, a scan line corresponding to a row
turns on the TFTs corresponding to the row, while other TFTs
corresponding to other rows are turned off by other scan lines
receiving a low-gate voltage Vlo. When the TFTs corresponding to a
row are all turned on, the data driver 10 outputs corresponding
video signals with gray scale values to m display units
corresponding to the row through the data lines D.sub.1 to D.sub.m
according to image data prepared for but not yet displayed. Each
time when the scan driver 11 finishes scanning all n rows, the
display of a single frame is complete. Therefore, the object of
displaying images is achieved by repeatedly scanning scan lines and
outputting video signals.
[0004] FIG. 2 is a schematic sectional view of the structure of the
display unit 100. A color filter CF is formed under an upper
substrate 20, and the common electrode CE is formed under the color
filter CF. The TFT T10 and the reference electrode RE are formed on
a lower substrate 21. A dielectric layer DL20 is formed over the
TFT T10 and the reference electrode RE. The pixel electrode PE is
formed on the dielectric layer DL20 and electrically connected with
the TFT T10 through a via hole H20. Referring to FIG. 2, the liquid
crystal capacitance Clc10 is formed between the common electrode CE
and the pixel electrode PE, and the storage capacitor Cs10 is
formed between the pixel electrode PE and the reference electrode
RE.
[0005] In practice, leakage of the storage capacitor Cs10 may be
induced by impurities between the pixel electrode PE and the
reference electrode RE, including a short circuit therebetween.
Accordingly, the pixel electrode PE and the reference electrode RE
have the same potential, which is the common voltage Vcom. Thus,
there is no voltage difference between the pixel electrode PE and
the common electrode CE, and liquid crystal molecules within the
liquid crystal capacitance Clc10 are not twisted. Thus, bright dots
appear when the LCD panel is in a normally white mode, resulting in
decreased image quality of the LCD.
SUMMARY
[0006] The present invention is directed to a display unit that is
configured to reduce bright dot effect in a display panel.
According to one aspect of the present invention, the display unit
comprises parallel coupled liquid crystal capacitance and storage
capacitor, which are biased at different voltage potentials. In
this configuration, in the event of a short in the storage
capacitor, the liquid crystal capacitance remains biased to reduce
displaying a bright dot in the display panel.
[0007] In one embodiment, the storage capacitor and the liquid
crystal capacitance are commonly coupled at one end to the pixel
electrode, and at the other end separately to different voltages.
In a further embodiment, the other end of the liquid crystal
capacitance is couple to a common voltage, and the other end of the
storage capacitor is connector to a low-gate voltage, wherein the
common voltage and the low-gate voltage are different.
[0008] In another aspect of the present invention, the display unit
provides an effective circuit structure that facilitates repair of
the circuit to reduce bright dot effect. In one embodiment, the
display unit includes a transistor switch (e.g., a TFT) coupled to
scan and data lines, and to parallel coupled liquid crystal
capacitance and storage capacitor at different voltage potentials.
In the event of a short between the drain and source of the
transistor, to repair the display unit to reduce bright dot, the
source or drain is decoupled from the rest of the circuit, and the
storage capacitor is shorted, so as to apply a voltage potential
difference across the liquid crystal capacitance.
[0009] An exemplary embodiment of a display unit is applied in a
display panel having a display array formed by at least one data
line and at least one scan line and comprises a switch unit, a
liquid crystal capacitance, and a storage capacitor. The switch
unit has a control terminal coupled to the scan line, an input
terminal coupled to the data line, and an output terminal coupled
to a pixel electrode. The liquid crystal capacitance is coupled
between the pixel electrode and a common electrode receiving a
common-voltage signal. The storage capacitor is coupled to the
pixel electrode and a reference electrode receiving a low-gate
signal. The voltage level of the common-voltage signal is different
from that of the low-gate signal.
[0010] Repair Methods for converting a bright dot to a dark dot in
a display unit are provided. The display unit comprises a switch
unit having a control terminal coupled to a scan line, an input
terminal coupled to a data line, and an output terminal coupled to
a pixel electrode, a liquid crystal capacitance coupled between the
pixel electrode and a common electrode, and a storage capacitor
coupled to the pixel electrode and a reference electrode. An
exemplary embodiment of a method comprises the steps of:
disconnecting the input terminal of the switch unit from the data
line; connecting the pixel electrode to the reference electrode;
wherein, a voltage level on the common electrode and a voltage
level on the reference electrode are different.
DESCRIPTION OF THE DRAWINGS
[0011] Display panels will become more fully understood from the
detailed description given hereinbelow and the accompanying
drawings, given by way of illustration only and thus not intended
to be limitative of the invention.
[0012] FIG. 1a is a schematic diagram of a conventional LCD
panel.
[0013] FIG. 1b is a schematic diagram of voltage coupled to scan
lines G.sub.1 to G.sub.n and common voltage coupled to the common
electrodes in the conventional LCD of FIG. 1a.
[0014] FIG. 2 is a schematic sectional view of the display unit 100
in accordance with one embodiment of the present invention.
[0015] FIG. 3a depicts an embodiment of a display panel in
accordance with the present invention.
[0016] FIG. 3b is a schematic diagram of voltage coupled to scan
lines G.sub.1 to G.sub.n and common voltage coupled to the common
electrodes in the display panel of FIG. 3a.
[0017] FIG. 4 is a flow chart of an embodiment of a repair method
in accordance with the present invention, for reducing a bright dot
in a display unit.
[0018] FIG. 5 is a schematic diagram of a display device deploying
display panel device disclosed in FIG. 3a.
[0019] FIG. 6 is a schematic diagram of an electronic device
deploying display device disclosed in FIG. 5.
DETAILED DESCRIPTION
[0020] Display panels are provided. In some embodiments, as shown
in FIG. 3a, a display panel 3 is in a normally white mode and
comprises a data driver 30, a scan driver 31, and a display array
32. The data driver 30 controls a plurality of data lines D.sub.1
to D.sub.m, and the scan driver 31 controls a plurality of scan
lines G.sub.1 to G.sub.n. The display array 32 is formed by
intersecting data lines D.sub.1 to D.sub.m and scan lines G.sub.1
to G.sub.n. The interlaced data line D.sub.m and scan line G.sub.n
correspond to a display unit, for example, interlaced data line
D.sub.1 and scan line G.sub.1 correspond to a display unit 300. For
each display unit, the equivalent circuit of the display unit 300
comprises a switch unit U3, a storage capacitor Cs30, and a liquid
crystal capacitance Clc30. In the embodiment of FIG. 3a, the switch
unit U3 can be a thin film transistor (TFT) T30, such as an N-type
TFT or a P-type TFT. Gate, drain, and source terminals of the TFT
T30 respectively serve as control, input, and output terminals of
the switch unit U3. The gate terminal of the TFT T30 is coupled the
scan line G.sub.1, the drain terminal thereof is coupled to the
data line D.sub.1, and the source terminal thereof is coupled to a
pixel electrode PE. The storage capacitor Cs30 is coupled between
the pixel electrode PE and a reference electrode RE, and the liquid
crystal capacitance Clc30 is coupled between the pixel electrode PE
and a common electrode CE.
[0021] FIG. 3b is a schematic diagram of voltage coupled to scan
lines G.sub.1 to G.sub.n and common voltage coupled to the common
electrodes in the display panel of FIG. 3a. Referring to FIGS. 3a
and 3b, in detail, the display unit 300 is given as an example. The
scan driver 31 outputs a scan signal with a high-gate voltage Vhi
to scan line G.sub.1 according to a scan control signal. When
receiving the scan signal, the scan line G.sub.1 turns on the TFT
T30 within the display unit 300. When the TFT T30 is turned on, the
data driver 30 outputs a corresponding video signal with a data
voltage Vdata to the display unit 300 through the data line
D.sub.1. At the same time, a voltage level of the pixel electrode
PE is equal to the data voltage Vdata. Conversely, when the scan
driver 31 outputs the scan signal with a low-gate voltage Vlo to
the scan line G.sub.1 according to the scan control signal, the
scan line G.sub.1 turns off the TFT T30.
[0022] Accordingly to one embodiment of the present invention, the
common electrode CE receives a common-voltage signal Scom with a
common voltage Vcom and the reference electrode RE receives a
low-gate signal Slo with the low-gate voltage Vlo. Levels of the
low-gate voltage Vlo and the common voltage Vcom are different. In
this embodiment, the level of the low-gate voltages is lower than
that of the common voltage Vcom. When a short circuit is produced
between the pixel electrode PE and the reference electrode RE due
to impurities therebetween caused during the process, a potential
of the pixel electrode PE is equal to the voltage level of the
reference electrode RE, the low-gate voltage Vlo. There is still a
voltage difference between the pixel electrode PE and the common
electrode CE, and liquid crystal molecules within the liquid
crystal capacitance Clc30 can still twist according to the voltage
difference. Thus, when the process of display units causes a short
circuit, the bright dots are reduced, improving image quality.
[0023] In manufacturing process of a display unit 300, a short
circuit may occur between the drain and source terminals of the TFT
T30, making the TFT T30 in always on state, and a bright dot would
appear on the display unit 300. FIG. 4 is a flow diagram of an
embodiment of a repair method for converting a bright dot to a dark
dot in a display unit of a display panel. Referring to FIGS. 3a and
4, when a bright dot appears in the display unit 300 due to the
short circuit between the drain and source terminals of the TFT
T30, the drain terminal of the TFT T30 is disconnected from the
data line D.sub.1 by a laser beam (step S40), so that, a video
signal on the data line D.sub.1 can not be transmitted to the
display unit 300. Then, the pixel electrode PE is configured to
connect with the reference electrode RE by a laser beam (step S41).
In other words, the voltage levels of the pixel electrode PE and
the reference electrode RE are the same. Thus, liquid crystal
molecules within the liquid crystal capacitance Clc30 can twist
according to a voltage difference between the pixel electrode PE
and the common electrode CE. Thus, the bright dot becomes less
bright or dark.
[0024] FIG. 5 schematically shows a display device 5 deploying
display panel 3 disclosed. Generally, the display device 5 includes
a controller 50, and the display panel 3 shown in FIG. 3a, etc. The
controller 50 is operatively coupled to the display panel 3 and
provides control signals, such as clock signals, start pulses, or
image data, etc, to the display panel 3.
[0025] FIG. 6 schematically shows an electronic device 6 deploying
display device 5 disclosed. The electronic device 6 may be a
portable device such as a PDA, notebook computer, tablet computer,
cellular phone, or a display monitor device, etc. Generally, the
electronic device 6 comprises an input unit 60 and the display
device 5 shown in FIG. 5, etc. Further, the input unit 60 is
operatively coupled to the display device 5 and provides input
signals (e.g., image signal) to the display device 5. The
controller 50 of the display device 5 provides the control signals
to the display panel 3 according to the input signals.
[0026] While the present invention has been described in terms of
various embodiments, it is to be understood that the present
invention is not limited thereto. On the contrary, it is intended
to cover various modifications and similar arrangements as would be
apparent to those skilled in the art. Therefore, the scope of the
appended claims should be accorded the broadest interpretation so
as to encompass all such modifications and similar
arrangements.
* * * * *